Scientists work up a disappearing act
ANNE MCILROY
SCIENCE REPORTER
The invisibility cloak that allowed Harry Potter to wander unseen through the halls of Hogwarts is no longer confined to the realm of fiction.
Researchers in Britain and the United States have published a theoretical blueprint for constructing an invisibility cloak using revolutionary new materials engineered to bend light and other electromagnetic waves in ways not seen in nature.
Sir John Pendry, a theoretical physicist at Imperial College London, says he may be able to make himself disappear in five years.
"Maybe I'm being optimistic," he says, "but I think it could happen."
It sounds like magic, but involves what are known as metamaterials, invented by Muggles (as non-wizarding folk are called in J.K. Rowling's books).
Metamaterials are engineered to include tiny physical structures -- metal coils, or rods shaped like aerials. Scientists have been able to "tune" these materials to bend electromagnetic waves in strange ways.
The plan, according to Sir John and his colleagues, is to channel light or other electromagnetic waves around an object, then restore them to their original trajectory on the other side.
"The cloak would act like you've opened up a hole in space," says David Smith, a professor of electrical and computer engineering at Duke University in North Carolina. He and Sir John co-authored a paper on cloaking devices published in this week's on-line edition of the journal Science.
Hide an object in a metamaterial cloak, Dr. Smith says, and electromagnetic waves would flow around it as water flows virtually undisturbed around a smooth rock.
The work is most advanced in channelling the radio waves used in radar, and researchers say they may be able to hide planes or ships from enemy radar systems. The military applications are important, and in the United States the work is funded in part by the Defence Advanced Research Projects Agency, which is responsible for developing new technology for the Department of Defence.
Dr. Smith is probably about 18 months away from developing a radar cloaking device using metamaterials, Sir John says.
But even more astounding -- at least for the average person -- is the idea of wrapping yourself in an invisibility cloak and disappearing.
Bending visible light is more difficult, the researchers say, because it has a much shorter wavelength than radio waves. This means the rods and coils would have to be extremely small, and perhaps built atom by atom with nanotechnology.
Is it doable? University of Toronto researcher George Eleftheriades thinks so. He designs metamaterials. "Something will come eventually, in a couple of years. It is not easy, but it is not impossible. And people are pretty smart when the stakes are high."
He described the blueprint published by Sir John and his colleagues as "very exciting, very ingenious work."
But it is not quite a match for the imagination of Ms. Rowling. In her books, Harry Potter's cloak is so thin, it fits in the inside pocket of his jacket. The real-life version would probably be quite a bit bulkier, Sir John says.
"We can't do gossamer thin," he says.
In the novels, Harry can see his silvery cloak, which he inherited from his father. But you wouldn't be able to see one made out of a metamaterial, Sir John says.
The young wizard can also see where he is going while wearing the cloak; that wouldn't be possible in the real-life version, Dr. Eleftheriades says.
Sir John and Dr. Smith first demonstrated metamaterials in 2000, and as many as three other teams are now researching how they could be used to make someone or something invisible. Another researcher, Ulf Leonhardt of the University of St. Andrews in Scotland, independently put forward a similar plan for an invisibility cloak, which was also published yesterday by the journal Science. |
